The present invention relates generally to disk drives and to a latch that inhibits the movement of a head stack assembly of a disk drive following a shock to the disk drive.
Disk drives are widely used in computers and data processing systems for storing information in digital form. Conventional disk drives include a head stack assembly, one or more storage disks and a spindle motor that rotates the storage disks. The head stack assembly includes an actuator motor, one or more actuator arms, and one or more head suspension assemblies. The actuator motor moves the actuator arms and the head suspension assemblies relative to the storage disks.
Each head suspension assembly includes a read/write head and a slider that xe2x80x9cfliesxe2x80x9d upon an air bearing in very close proximity to the rotating storage disk. Unfortunately, contact between the slider and the storage disk can result in damage to the storage disk or the head suspension assembly.
In some disk drives, the actuator motor positions the slider over a landing zone as power is removed from the spindle motor. The landing zone can be a ramp that is positioned near the storage disk. Alternately, the landing zone can be a textured, non-data region of the storage disk.
However, even when the slider is positioned safely in the landing zone, a sufficient force or shock to the disk drive can cause the slider to move from the landing zone onto a data storage surface of the storage disk. Conventional disk drives attempt to address this problem with a latch that inhibits movement of the head stack assembly, and thus the slider, relative to the storage disk during non-rotation of the storage disk. Unfortunately, existing latch designs are not altogether satisfactory.
For example, a wind vane latch is commonly used in disk drives. Normally, the wind vane latch is biased to a closed position that inhibits movement of the head stack assembly. The wind vane latch relies upon airflow generated by rotation of the storage disks to move the wind vane latch from the closed position to an open position that allows for movement of the head stack assembly. However, wind vane latches have not been used in relatively small drives such as notebook drives or microdrives due to the limited airflow generated by the relatively small rotating storage disks.
Other types of normally closed latches require a significant amount of energy to move and/or maintain the latch in the open position. Moreover, the use of normally closed latches can be problematic with ramp type disk drives that require that the slider be loaded onto the storage disk within a tightly specified velocity window. More specifically, the normally closed latch may still be in the closed position and inhibiting motion of the head stack assembly when the storage disk is being accelerated through the desired speed range for loading the slider. Accordingly, normally open latches are generally preferred for disk drives having ramps. With a normally open latch, upon a sufficient shock to the disk drive, the latch temporarily closes to inhibit movement of the head stack assembly for a somewhat arbitrary, brief time period. Subsequently, the latch returns to the open position. However, the temporary closure of the latch may be insufficient after a shock, to inhibit movement of the head stack assembly caused by post shock out-of-phase bouncing of the head stack assembly and the latch. This is especially true for mobile products, which are subjected to more severe and complex shock pulses.
Bi-stable latches have also been developed. In the absence of any external force or disturbance, a bi-stable latch has two different preferential resting positions, namely the open position and the closed position. Conventional bi-stable latches can include a separate motor to move the latch between the positions. Unfortunately, the use of another motor increases the power demand of the disk drive, generates unwanted heat, increases complexity and requires extra electrical connections.
In light of the above, the need exists for a reliable, simple, and efficient latch that effectively inhibits damage to the head suspension assemblies and the storage disks. Another need exists to provide a disk drive including a latch that inhibits movement of the head stack assembly during non-rotation of the storage disks. Still another need exists to provide a latch for a disk drive that is relatively easy and cost effective to manufacture, assemble and use.
The present invention is directed to a disk drive that includes a storage disk, a stop, a head stack assembly and a latch. The latch includes a latch arm that is movable between a closed position that inhibits movement of the head stack assembly in a direction away from the stop, and an open position that allows for movement of the head stack assembly away from the stop. The latch also includes a first retainer and a spaced apart second retainer that are secured to the latch arm. The first retainer selectively retains the latch arm in the open position, and the second retainer selectively retains the latch arm in the closed position. The bi-stable latch provides protection against out-of-phase bouncing of the head stack assembly and the latch.
The head stack assembly includes an actuator motor that moves the head stack assembly relative to the storage disk. In one embodiment, the first retainer interacts with the actuator motor to urge the latch arm to the open position and the second retainer interacts with the actuator motor to urge the latch arm to the closed position. Thus, both retainers interact with a magnet component that is already present in the drive.
The latch can also include a mover that contacts the latch arm upon a sufficient shock to the disk drive. The mover causes the latch arm to move from the open position to the closed position. Additionally, the latch arm can include a first mover contact and spaced apart, second mover contact. The mover engages the first mover contact upon a sufficient force or shock in a first direction to the disk drive, and moves the latch arm to the closed position. Further, the mover engages the second mover contact upon a sufficient force or shock in a second direction to the disk drive, and moves the latch arm to the closed position. With this design, the same mover moves the latch to the closed position if the shock is in the first direction or if the shock is in the second direction.
In one embodiment, when the latch is in the closed position, movement of the head stack assembly toward the stop causes the head stack assembly to engage the latch arm and move the latch arm from the closed position to the open position. With this design, a separate motor is not necessary to move the latch arm from the closed position to the open position.
The present invention is also directed to a method for selectively retaining a head stack assembly near a stop of a disk drive.